按要求写句子。

《蒙娜丽莎》是世界上最杰出的肖像画。

缩句：____

增加：在缺词处加一个漏字符号（∧），并在其下面写出该加的词。

删除：把多余的词用斜线（\）划掉。

修改：在错的词下划一横线，并在该词下面写出修改后的词。

注意：1）每处错误及其修改均仅限一词；

2）只允许修改10处，多者（从第11处起）不计分。

Dear Tom,

    I'm happy to get from your letter and knew you're coming to China.

    Among the two trips to the Yangtze River and Mount Tai, both are high recommended (推荐). Personally, I prefer the tour along the Yangtze, longest river and one of the mother river of Chinese civilization. You can learn a tot about the history of China and Chinese people. Moreover, the scenery along the river are amazing, with many well-know sightseeing spots. That's because I think the trip along the Yangtze will be a better choice.

    I hope your suggestion will be of some help and you'll have a good time in China.

Yours,

Li Hua

189与某数的最大公约数是21，最小公倍数是378，这个数是____ ．